It is known that propeller driven watercraft or aircraft, rotor aircraft, and jet propelled watercraft or aircraft each have their associated performance strengths and weaknesses. For example, propeller driven aircraft are useful when slow loitering flight is desired, for example, when it is desired both to observe the ground below, and when flight over long range is desired. Conventional rotor aircraft, such as helicopters, are useful for shorter range flights, again where slow speed may be useful, and where vertical take-off and landing may be required. It is also now known that it is feasible to combine the useful traits of both propeller driven aircraft and rotor aircraft, for example, as displayed in the V22 Osprey.TM. aircraft manufactured by Boeing et al. Jet propelled aircraft are of course well adapted for high speed, extremely long range and extremely high altitude flights of which propeller driven aircraft and rotor aircraft are not capable.
Combining propellers with turbine jet engines in the case of aircraft, or with impellor water thrust motors in the case of watercraft, may take advantage of the performance of both forms of propulsion. The problem in implementation of this combination in aircraft is that propellers and rotors will, during transonic and supersonic flight, not only significantly increase drag but will present a structural hazard unless suitably stowed. Similarly, at high speeds, propellers on watercraft only add drag with no contribution to thrust. In the prior art, there has been at least one attempt to provide for folding of rotor blades in flight so as to store the blades during jet propelled flight, namely, U.S. Pat. No. 5,085,315 which issued Feb. 4, 1992 to Sambell for a Wide-range Blade Pitch Control for a Folding Rotor. The pitch control mechanism of Sambell is adapted for use in rotary wing aircraft where the mast and rotor may be pivoted between a horizontal stored position and a vertical helicopter mode position. A star gear is connected to a pitch horn so as to amplify to the rotors, control motions transmitted to the pitch horns through a push-pull control tube parallel to either the folding axis of the rotor blade or the mast axis.
Applicant is also aware of U.S. Pat. No. 5,102,301 which issued Apr. 7, 1992, to Morrison for Variable Pitch Propeller Blades, Hub and Drive and Adjusting Mechanism Therefor. Morrison discloses propellers used in stern drive propulsion for boats where the propellers are of variable pitch, the pitch adjusted by a pitch adjusting mechanism. In one embodiment, propeller blades are mounted on a hollow drive shaft connected to the second rotatable drive shaft by means of a set of matching bevelled gears. The propellers are turned so as to propel the boat by rotation of the shafts by an outboard motor or inboard motored power train. A pitch adjusting shaft may be moved linearly within the hollow drive shaft to thereby cause the pitch of the blades to be changed. The pitch adjusting shaft is slid linearly within the hollow drive shaft by a pitch control rod driving an L-shaped pivot. Linearly driving the pitch control shaft relative to the hollow drive shaft rotates the propeller blades about stub axles by means of mechanical linkages on the end of the pitch adjusting shaft rotate lever arms or lobes also rotatably mounted on the stub axles and rigidly mounted to the blades.
Applicant is also aware of U.S. Pat. No. 3,142,455 which issued Jul. 28, 1964 to Wilford for a Rotary Vertical Take-off and Landing Aircraft. Within the rotor blade head of Wilford, is disclosed an outer gimbal member freely and rotatably mounted on a universally mounted inner swash plate member. A number of cyclic pitch control arms or linkages are universally connected to the swash plate member, spaced 90 degrees apart from each other. The other gimbal member is operatively coupled to each of the rotor blades by a pitch control link universally connected to the outer gimbal member and pivotally connected to each shank of the blades by means of a link which in turn is pivotally connected to a pitch control arm rigid with an extending forwardly of the blade and lying within its chordal plane. Each of the rotor blade pitch control links at one end is universally connected to the outer gimbal member and blade pitch lever at a point forwardly of the leading edge and direction of rotation of the related rotor blade. The angle of attack of the rotor blades may thereby be adjusted. The rotor blades may be controlled throughout a folding operation between a coning or trailing arrange and an extended propulsive position by means of the swash plate assembly which provides the cyclic and collective pitch control of the blades.